Cadillac CTS First Generation Forum - 2003 - 2007 Discussion, need a quick answer, which trans cooler line is supply and which is return. !!! in Cadillac CTS Coupe, Sport Sedan and Sport Wagon Forums; I need a quick answer, anyone know which cooler line is the supply line and which is the return ? ...

Re: need a quick answer, which trans cooler line is supply and which is return. !!!

Originally Posted by briggy

I need a quick answer, anyone know which cooler line is the supply line and which is the return ? Ideally I need to know from the transmission conenction side thanks.

Hey Briggy the best way I know is to use a hand held infrared thermometer on the transmission lines after driving it a little while. The hotter one is supply and or the cooler one is return. If you don't have one I know Harbor Freight has them pretty cheap. Found this really cheap one online > http://www.tmart.com/Infrared-Thermo...FYo9Qgodwl0A9Q

If its for the external cooler it doesn't really matter. The cooler doesn't have an in and out. As long as the fluid is going through it then it's all good. If it's for another reason then it's as stated above. Heat gun on the two lines at operating temp. Hot line is the outlet if the tranny. If you don't have a heat gun or your car is apart then I can let you know tomorrow. I have an infrared gun and can give you an answer in the morning. Pam me if you need that info.